Carburized steel part having excellent low cycle bending fatigue strength

Inactive Publication Date: 2012-03-15
NIPPON STEEL & SUMITOMO METAL CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

[0042]If using the carburized steel part having excellent low cycle bending fatigue strength of the present invention, it is possible to greatly reduce the size and lig

Problems solved by technology

However, in each carburized steel part, the low cycle bending fatigue strength do

Method used

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  • Carburized steel part having excellent low cycle bending fatigue strength
  • Carburized steel part having excellent low cycle bending fatigue strength
  • Carburized steel part having excellent low cycle bending fatigue strength

Examples

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Example

Example

[0136]Next, examples of the present invention are explained, but the conditions of the examples are illustrations of conditions which are employed for confirming the workability and advantageous effects of the present invention. The present invention is not limited to the illustrations of examples.

[0137]The present invention may employ various conditions so long as not outside the gist of the present invention and achieving the object of the present invention.

Example

[0138]Steel materials of the compositions of ingredients which are shown in Table 1 and Table 2 were drawn, then soaked and normalized to prepare roughly worked test pieces for low cycle bending fatigue tests and roughly worked test pieces for wear tests.

TABLE 1TestComposition of ingredients (mass %)no.ClassCSiMnPSNAlOB1Inv. ex.0.350.260.800.0100.0150.0120.0300.0010—2Inv. ex.0.401.000.800.0090.0150.0060.0390.0009—3Inv. ex.0.310.900.810.0100.0150.0060.0370.00120.00154Inv. ex.0.600.240.730.0080.0300.0060.0210.0006—5...

Example

[0141]A roughly worked test piece of Test No. 26 (comparative example) was carburized in a conversion type gas carburization furnace at 930° C. for 5 hours, then were quenched by oil at 220° C.

[0142]A roughly worked test piece of Test No. 27 (comparative example) was carburized in a conversion type gas carburization furnace at 930° C. for 5 hours, then were quenched by oil at 30° C., then tempered for 1.5 hours.

[0143]Note that, the carbon potential at the time of carburization was adjusted to 0.5 to 0.8 in range and the tempering temperature was adjusted to 150 to 300° C. in range to adjust the surface hardness and the core hardness.

[0144]After heat treatment, roughly worked test pieces for low cycle bending fatigue test use were machined to remove only the carburized layer at the side surfaces to prepare 13 mm square notched test pieces 1 (low cycle bending fatigue test pieces) shown in FIG. 1.

[0145]For roughly worked test pieces for wear tests, just the gripping parts were machine...

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Abstract

A carburized steel part having excellent low cycle bending fatigue strength which is comprised of a steel material which contains, by mass %, C: 0.1 to 0.6%, Si: 0.01 to 1.5%, Mn: 0.3 to 2.0, P: 0.02% or less, S: 0.001 to 0.15%, N: 0.001 to 0.03%, Al: 0.001 to 0.06%, and O: 0.005% or less and has a balance of substantially iron and unavoidable impurities and which is carburized and quenched, and then tempered, which steel part has a surface hardness of HV550 to HV800 and a core hardness of HV400 to HV500.

Description

TECHNICAL FIELD[0001]The present invention relates to a carburized steel part having excellent low cycle bending fatigue strength.BACKGROUND ART[0002]Parts for machine structures, differential gears, transmission gears, toothed carburized shafts, and other gears sometimes break at the tooth bases after low cycle fatigue (fatigue in region of several hundreds to several thousands of cycles) due to sudden starts and sudden stops of the vehicles. In particular, greater improvement of the low cycle fatigue strength is being sought for differential gears and for transmission gears.[0003]In the past, as the steel material for the above steel parts, JIS SCr420, SCM420, and other around C: 0.2% case hardened steel has been used to secure toughness of the core. “Carburizing and quenching” and around 150° C. low temperature tempering are used to form an around C: 0.8% tempered martensite structure on the surface and to improve the high cycle bending fatigue strength and wear resistance.[0004]...

Claims

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Application Information

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IPC IPC(8): C22C38/02C22C38/06C22C38/08C22C38/14C22C38/12C22C38/16C22C38/04C22C38/38
CPCC21D1/06C21D9/32C21D2211/004C22C38/002C23C8/22C21D1/68C21D2211/008
Inventor KOZAWA, SHUJIKUBOTA, MANABUKADA, OSAMUNISHIKAWA, MOTOHIROTANAKA, TAKASHITSUNEKAGE, NORIMASA
Owner NIPPON STEEL & SUMITOMO METAL CORP
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